Mycobacterium tuberculosis Infection by QuantifERON-TB Gold Plus


Abbrev Code:QFT   
Order Code:LAB8219Order Name:Quantiferon TB Gold Plus
Synonyms:QTF; Latent TB; Latent tuberculosis; LTBI; Mycobacteria; Quantiferon Gold Plus; Interferon Gamma Release Assay (IGRA); QPLUS
Methodology:Interferon-y release assay (IGRA) by chemiluminescence immunoassay
CPT Codes: 86481 x1
Turnaround Time:Performed Mon-Fri; results are reported within 2-4 days.


Collection Instructions

Specimen:Blood
Optimal Volume:1.0 mL in each of four tubes from QTB Plus collection kit.
Minimum\Peds Volume:0.8 mL in each of four tubes from QTB Plus collection kit.
Container:QuantiFERON QTB Gold PLUS Collection Kit (available from lab)
Collection Instructions:QFT tubes should be the last tubes collected during a blood draw.  
  1. It is recommended to collect the QFT tubes with a syringe and transferring the blood into the tubes up to the fill line. QFT tubes can be collected in any order.
  2. If a syringe is not available, the use of butterfly needle is NOT recommended. If a butterfly is required, first collect other collection tubes or use a "purge" tube to ensure that the tubing is filled with blood prior to the first QFT tube. Then continue with the collection of the QFT tubes.
  3. Immediately after filling tubes, shake them ten (10) times just firmly enough to ensure the entire inner surface of the tube is coated with blood, to solubilize antigens on tube walls. Over vigorous shaking may cause gel disruption and could lead to aberrant results.
  4. Label each tube using its respective long name label (QGREY on the grey top tube, QGREEN on the green top tube, QYELLO on the yellow top tube and QPURPL on the purple top tube). Do not use small peon labels. Ensure that the fill line indicator and blood volume remains visible for assessment.
  5. Following labeling, filling, and shaking, the tubes must be transferred to a 37°C+1°C incubator as soon as  possible, and within 16 hours of collection.
Causes for Rejection:Specimens other than those collected and processed according to instructions in the QuantiFERON QTB Gold PLUS Collection Kit.


Processing and Shipping

Specimen Processing:Samples are sent to the East Core Laboratory. East Core will process and send test ready sanples to Specialty Core for testing. 

Order Instructions:
  1. Maintain tubes at room temperature until incubation. It is recommended that incubation start as soon as possible and must be started within 16 hours of collection.
  2. INCUBATE all 4 tubes upright at 37°C for 16-24 hours. If delayed from collection, re-mix tubes by inverting ten (10) times before incubation. (Improper incubation may cause erroneous results. Humidity and CO2 are not required.)
  3. After incubation, centrifuge tubes for 15 minutes at 3000 RCF (g).
  4. Place all 4 tubes together back in the original QTB transport bag and label "incubated".
  5. Store and ship at refrigerated temperature.
  6. IMPORTANT: East Core will process and send test ready samples to Specialty Core for testing.
Shipping Instructions:Ship non-incubated samples at room temperature within 12 hours.
Ship incubated samples at refrigerated temperatures in a labeled QTB Plus transport bag.
Test Performed at or Referral Lab (Final destination (UMMC East Core) will process and send to testing lab (UMMC Specialty Core)


Interpretive

Reference Range:By report.
Use:Aids in the diagnosis of Mycobacterium tuberculosis infection, including latent tuberculosis infection (LTBI) and tuberculosis (TB) disease. QFT-G can be used in all circumstances in which the tuberculin skin test is currently used, including contact investigations, evaluation of recent immigrants who have had BCG vaccination and TB screening of health care workers and others, undergoing serial evaluation for M. tuberculosis. However, caution should be used when testing certain populations because of limited data in the use of QFT-G.
New guidelines around TB testing were published on Dec 12, 2016, in Clinical Infectious Disease®2017;64(2):111-5. The new guidelines were the outcome of a task force made up of the American Thoracic Society (ATS), the US Centers for Disease control and Prevention (CDC), and the Infectious Diseases Society of America (IDSA). These three organizations joined forces to broaden the preferential recommendation of modern blood-based TB tests over the 100 year old tuberculin skin test (TST). The task force recommends performing an interfon-g release assay (IGRA) rather than a tuberculin skin test (TST) in individuals >5 years old who meet the following criteria:
  • Those likely to be infected with Mycobacterium tuberculosis
  • Anyone with low or intermediate risk of disease progression
  • Those who it has been decided the LTBI testing is warranted
  • BCG-vaccinated individuals or those unlikely to return for their TST reading


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